Generally, a semiconductor element is manufactured by performing various manufacturing processes, such as a deposition process, a photograph process, and an etching process, and an ion implantation process, to a silicon wafer.
For example, a silicon wafer has various process layers during a manufacturing process, and a process of selectively removing and patterning some of such process layers, and then depositing an additional process layer on a surface of a preformed process layer, can be repeatedly performed.
Such a process layer may be an insulation layer, a gate oxide layer, a conduction layer, and a metal or glass layer, etc.
Herein, in a specific process, an uppermost surface of a process layer preformed on a wafer is preferably flat so as to allow a succeeding process layer to be deposited thereon.
Therefore, a silicon wafer passes through a polishing process for polishing a preformed process layer to be flat, so that a succeeding process can safely be performed thereon.
Particularly, a wafer polishing process is a process for flattening a surface of a wafer. For an representative example, a chemical-mechanical polishing/planarization (CMP) process has been suggested, in which a chemical slurry is applied on a polishing pad to make friction contact with a surface of a wafer, and in a state of a surface of the wafer being pressurized on the polishing pad, the wafer and the polishing pad perform relative friction movement each other so as to safely flatten a surface of the wafer.
Meanwhile, an equipment for performing a CMP process, as described above, is disclosed in Korean Patent No. 490266 filed in the name of the present applicant.
FIG. 1 is a schematic view illustrating a construction of a conventional CMP equipment. With reference to FIG. 1, the conventional CMP equipment may include a platen 10 on which a polishing pad which makes surface contact with a surface of a wafer so as to make physical friction against the surface of the wafer, is mounted, a polishing head 20 for fixedly holding a wafer and pressing down the wafer placed on the polishing pad 11 so as to make the wafer be in fiction contact with the polishing pad 11, a spindle 30 for rotating the polishing head 20 while pressing the polishing head 20 holding the wafer toward the polishing pad 11, and a loading unit 40 for loading a wafer to be polished on the polishing head 20 or unloading the wafer from the polish head 20 after the polishing, etc.
In such loading unit 40, a wafer is placed on an upper surface of a loading plate 42 installed at an uppermost part of a loading cup 41 so as to be supported by a loading plate, and the wafer placed between the loading plate 42 and the polishing head 20 is held by or separated from them relative to each other, and an arm 44 connected with the loading cup 41 rotates toward the polishing head 20 about a rotational shaft 43 and moves up and down.
Meanwhile, additionally to the structure, the conventional CMP equipment has a disadvantage in that alien substances including slurry particles, etc., which are generated while polishing a wafer, settle in a groove of the polishing pad 11, so that a scratch is generated in the wafer, or the lifetime of the polishing pad 11 is reduced.
Then, the conventional CMP equipment may further include a cleaning device for removing alien substances including slurry particles on the polishing pad 11.
For example, the cleaning device is assembled with a lower surface of a spindle 30 so as to revolve above the polishing pad 11 along with the polishing head 20 by the rotation of the spindle 30. The cleaning device injects cleaning liquid, such as deionized water or ultrapure water, etc., on the polishing pad 11 so as to remove alien substances, including slurry particles on the polishing pad 11.
However, since the conventional cleaning device for the CMP equipment injects only cleaning liquid in a single manner, the rate of removing slurry articles or alien substances is low, so that it is impossible to prevent scratching of a wafer and lifetime-reduction of the polishing pad, as mentioned above.
Furthermore, in the conventional CMP equipment, friction heat caused by friction force is generated in the polishing pad while a polishing process is performed, so that the polishing pad has a high temperature.